1. Field of the Invention
The present invention relates generally to read head portions of magnetic heads for hard disk drives, and more particularly to read heads having anti-parallel coupled magnetic structures at end regions of the free layer.
2. Description of the Prior Art
One well known way to increase the performance of hard disk drives is to increase the areal data storage density of the magnetic hard disk. This can be accomplished by reducing the written data track width, such that more tracks per inch can be written on the disk. To read data from a disk with a reduced track width, it is also necessary to develop sufficiently narrow read head components, such that unwanted magnetic field interference from adjacent data tracks is substantially eliminated.
The standard prior art read head elements include a plurality of thin film layers that are deposited and fabricated to produce a GMR read head, as is known to those skilled in the art. Significantly, where the width of the thin film layers that comprise the GMR read head is reduced below certain values, the magnetic properties of the layers are substantially compromised. To overcome this problem, GMR read heads have been developed in which the thin film layers have an ample width and the electrical leads are overlaid on top of portions of the thin film layers. This lead overlaid configuration has the effect of creating an active read head region having a width that is less than the entire width of the deposited layers, such that the magnetic properties of the thin film layers can be preserved. Thus, in the lead overlaid GMR read heads of the prior art, active magnetic layer portions exist between the electrical leads and passive magnetic layer portions exist in the end portions of the layers beneath the electrical leads.
A problem that has been recognized with regard to such prior art lead overlaid read heads is that the passive region of the magnetic layers of the read head, and particularly the free magnetic layer, is not entirely passive. That is, external magnetic fields, such as from adjacent data tracks, create magnetic field fluctuation and noise within the passive regions of the free magnetic layer beneath the electrical leads. Thus, noise and side reading effects continue to be a problem with lead overlaid GMR read heads. The present invention seeks to solve this problem by pinning the magnetization of the free magnetic layer by adding an anti-parallel coupled layer structure on top of the end regions of the free layers to provide magnetostatic bias to the end regions, thus stabilizing the end regions as well as the central free layer region, and reducing noise and side reading effects.
The present invention is an improved magnetic head for a hard disk drive including a read head structure in which the magnetic fields of the end regions of the free magnetic layer are stabilized by a magnetostatic bias provided by an anti-parallel coupled layer structure that is fabricated on top of the end regions. In one embodiment of the present invention the anti-parallel coupled layer structure includes thin film layers comprised of materials such as CoPtCr, Ru and CoPtCr that are deposited on top of the end regions of the free layer. The thickness of the CoPtCr layers is particularly selected to create a magnetostatic bias that acts to pin the magnetic fields in the end regions of the free layer. The operational characteristics of the read head are improved because the end regions of the free layer are magnetically stabilized and thus not affected by side reading magnetic fields from adjacent data tracks. Noise and side reading effects are thereby reduced and the performance of the read head is thereby improved. In an alternative embodiment of the present invention layers of CoFe are deposited on each side of the Ru layer to improve the anti-parallel coupling of the CoPtCr layers. This further stabilizes the magnetostatic field of the layers, such that the magnetic fields within the end regions of the free layer are thereby rendered less sensitive to side reading and noise, and an improved magnetic head is thereby produced.
It is an advantage of the magnetic head of the present invention that a read head structure has been developed with reduced noise and side reading problems.
It is another advantage of the magnetic head of the present invention that a read head structure has been developed having stabilized magnetic fields in the end regions of the free magnetic layer thereof.
It is an advantage of the hard disk drive of the present invention that it includes a magnetic head having a reduced read track width with reduced side reading and noise.
It is another advantage of the hard disk drive of the present invention that it includes a magnetic head having a read head structure having stabilized magnetic fields in the end regions of the free magnetic layer thereof.
These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art upon reading the following detailed description with makes reference to the several figures of the drawings.